1. Field of the Invention
The present invention relates to a lighting system for a vehicle, such as a motorcycle. More particularly, the present invention relates to a vehicle lighting system having reduced number of parts and simplified structure including application of a single filament bulb as a winker lamp and a position lamp.
2. Description of the Background Art
There are known lighting systems for vehicles, such as motorcycles, in which a single filament bulb is sometimes used as both of a winker lamp and a position lamp. In these systems, when the single filament bulb is operated as a winker lamp, current is supplied at a duty ratio of 100% to the single filament bulb, but when the single filament bulb is operated as a position lamp, current is supplied at another duty ratio of 25% to the single filament bulb thereby making it possible to achieve two functions using a single lamp. The lighting changeover between a winker lamp and a position lamp is performed by operation of a relay.
An example of such a known lighting system, having a single filament bulb used as both of a winker lamp and a position lamp, is disclosed in the Japanese Patent No. 2706605.
As shown in FIG. 5 of this application, a lighting system 100 of the Japanese Patent No. 2706605 includes a left front lamp FL, a left rear lamp RL, a right front lamp FR, a right rear lamp RR, a left indicator lamp INDL and a right indicator lamp INDR, a position winker relay (a relay unit) 110, a winker hazard holding relay 120, a winker switch 130, and a hazard switch 140. The left front lamp FL and the right front lamp FR are used as winker lamps as well as position lamps.
In the system of the Patent Document No. 2706605, on an electrical connection line which interconnects the hazard switch 140 and the left rear lamp RL, right rear lamp RR left front lamp FL, and right front lamp FR, four diodes D1, D2, D3 and D4 are respectively provided. For example, a diode D1 is operatively disposed on an electrical connection between the hazard switch 140 and the left rear lamp RL. Further, the position winker relay 110 includes an Integrated Circuit (IC) 111 for exclusive use as a lighting control section, a left front driver 112, a right front driver 113 and a rear driver 114.
When an ignition switch is on, current is selectively supplied from a vehicle-carried battery (not shown) to the left front lamp FL, left rear lamp RL, right front lamp FR and right rear lamp RR in response to changeover of the winker switch 130 or the hazard switch 140.
The left front lamp FL, left rear lamp RL, right front lamp FR and right rear lamp RR are in the form of a single filament bulb. In the lighting system of the Japanese Patent No. 2706605, lighting for a position lamp is performed when no input is provided to the left and right rear lamps RL, RR, but flickering for a winker lamp is performed when an input is provided to one of the left and right rear lamps RL, RR. In this instance, if an intermittent input is provided to both of the left and right rear lamps RL, RR for hazard indication, then flickering for a winker lamp and lighting for a position lamp are performed simultaneously, and lighting in a glimmering state is provided.
Thus, in order to make it possible to definitely distinguish flickering or lighting of winker lamps and position lamps and indication of hazard lamps, the position winker relay 110 and the winker hazard holding relay 120 are used for single filament bulb lighting so that lighting for hazard lamps can be performed.
In the lighting system as shown in FIG. 5, since two different relays (having different specifications from each other), that is, the position winker relay 110 and the winker hazard holding relay 120 are used, the management of the lighting system becomes complicated as the increased number of parts are required for such systems. Particularly, the IC 111 for exclusive use included in the position winker relay 110 makes an obstacle to standardization of parts. Further, it is necessary to used four large capacity diodes D1, D2, D3 and D4, through which current from the battery flows, and such large capacity diodes may be expensive and may impose assembling problems.
Therefore, there is a need for a lighting system for a vehicle which does not require a winker hazard holding relay or a diode of a large current capacity to improve the layout performance and which allows further standardization of components. Accordingly, in view of the above-mentioned drawbacks of the known lighting systems, it is an object of the present invention to provide a simplified vehicle lighting system requiring reduced number of components.